I need some advise please

Hi all. I am new to the forum but i have been browsing for quite a while and admiring some fantastic photos. I have been interested in astrophotography for a while. I have already been taking photos of the moon and trying my hand at star trails. I love the moon and wish to get closer and take some better pics. I use a tamron 70-300mm lens on a canon 550D. I am unsure as to weather i should purchase a Kenko 2x teleconverter for my Tamron lens or should i purchase Celestron 52268 C90 or is there some other piece of equiptment i should be looking at that will enable me to view the moon plus take great photos. The other downside is that i only have a £250 budget.
Thanks
Sharon

Suggestion: neither. The 2x converter will lose two stops of light AND will compromise your image quality. Try to avoid these things in astrophotography. As for the Clestron C90, well, years ago I tried three different telescopes and not one of them was free of (I can't remember which) optical aberration, but the images of the moon I tried with them all were hopeless. Therefore, I don't know about now, but I still tend to avoid them.

In fact, I then bought a Tamron 500/8 and its 2X converter. The moon images with that were heaps better. NOW I'M NOT telling you to get one of these, but just be aware of what you're getting.

And see what others say.
Am.

Thanks Am
So what your saying is that a 2xtc will be no good on a tamron 70-300mm but it would work better on a mirror lens? Is this my only option with £250. This is what i can achieve with my 70-300 but i want to get closer
Thanks
Sharon

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I have a simple solution: Canon 500mm F4L IS II =)

It would be a really simple solution if i had that kind of money. Infact if i had that kind of money spare i would buy a rocket, now that would get me closer
Sharon

I've taken great shots of the moon with my 70-200 plus Kenko Pro teleconverter. The key is to use a tripod and longer exposure at a higher ISO to make up for the loss of light the teleconverter causes.

Here's one I took:

Thanks Jon that has been very helpful
Sharon

You see that colour fringing at the edge of the lunar disc? That will likely be more pronounced with (esp. any old) teleconverter.

Look, there are some pretty cheap mirror lenses, too. Recently I heard of an Opteka f=500/6.3.
Now I **DON'T KNOW** anything about them at all and I'm not recommending it.
Here's a link to one here, with a local price you can multiply by 2/3 for pounds.

The things about mirror lenses is that they can be GOOD/BAD, USEFUL/LIMITED (in application).

And something to think about: each 100mm of focal length will give about 1mm image size for the sun/moon.

Basically, get the best you can afford WITHOUT wasting money. I'd say that your 250 would get a Tamron500/8 and matched teleconverter, but check. If you could get a good refractor lens, ie. glass, I think you'd be better off for contrast and general useability, even if it's not as compact as a mirror lens. You may not need (though it's top line stuff) one like iluka suggested above.

Ultimately, if the 2x converter is cheap and right there now, I suppose you could try it. Just make sure that it will work with your particular lens.
Am.

Thanks Am
I ordered the celestron 52268 C90 for the kids as i hate them touching my equipment when i have it set up and they want to look. I have a chance of a getting a second hand teleconverter so going to give it a try. In the mean time i am going to save for the sigma 170-500mm lens
Thanks Sharon

Sharon, I definitely would stay away from mirror lenses. There is a reason they are cheap. They have a large central obstruction and the images they produce are not sharp at all. Most of them are horribly slow, although the one in the link above is not too bad at f6.3. Still, I think you would do much better with the set up you are contemplating. Any slight color fringing can be easily removed with a photo editor like Photoshop, Elements, Lightroom, etc.

I use a teleconverter and have never had any problems with fringing or false color. Keep in mind the links to the images I posted were taken handheld. Had I used a tripod they would have been sharper. But the moon was such a rich color that night that I grabbed my camera, bumped up the ISO, added the teleconverter and shot away.

The teleconverter I use is Kenko Pro and I find it to be as good as Canon's. It will work on non L lenses, whereas Canon's converter will not. Hope this helps.

Thank you Jon
The kenko converter is a MC7 C-AF 2X teleconverter. It's not the pro version but hopefully will still do a decent job. I have actually seen some shots on here taken with the sigma 170-500mm plus a teleconverter and they look amazing.
Sharon

Jon do you know what the difference is between the
Kenko Teleplus DGX 2X MC7 Teleconverter
Kenko Teleplus 2x MC7
i think the DGX keeps it in focus and shows true focal lengh. Do you know if this is really needed as the one i'm looking at is not the DGX model
Thanks Sharon

Sharon, the DGX version is not compatible with crop sensor cameras whereas the MC7 should work just fine. Keep in mind autofocus will have a limited range with which it will work unless you tape the pins. You can do a Google search and find articles explaining how to do that and have autofocus work (a little slower) if the lens is stopped down.

Will this be okay for my canon 550D
Kenko 2x Teleplus PRO 300 DGX Teleconverter Canon EOS EF
Thanks
Sharon

Sharon,
I'm not sure if it's applicable to moon shots but I went through a similar learning process when I was shopping for a super-telephoto. After buying a couple of lenses and converters, I quickly learned that getting closer isn't always better. It's the net result of the combination of image quality and focal length that makes the difference.

For example, an inexpensive converter might allow the moon to fill your whole frame with a low quality image. On the other hand, the inexpensive Canon 55-250mm lens won't magnify the moon as much but the image quality might be good enough that you can crop out everything but the moon and still have a better photo.

Sorry I don't have more specific advice, but I learned (the hard way) that increasing magnification doesn't necessarily produce a better photo. (Stars are a whole different animal. Again, I don't have any experience in the field but I remember reading that there are some unexpected factors that are important to consider when shooting photos of stars.)